This invention relates to the preparation of novel antiozonant as well as antioxidant based on functionalized hindered phenol and the process for the preparation thereof. More particularly it relates to the said absorber having a formula 1: 
wherein R1 is tert-butyl and R2 and R3 are C1 to C8 linear or branched alkyl. Still more particularly, the invention relates to novel antiozonant as well as antioxidant based on functionalized hindered phenols and useful as condensable monomer for the synthesis of many polymers with in-built antioxidants and the process for the synthesis thereof.
Co-pending application Ser. No. 10/396126 relates to the novel antiozonant as well as antioxidant based on functionalized hindered phenol obtained by the process of this invention.
More particularly the present invention relates to the preparation of said novel antiozonant and antioxidant, using compound of formula 2 
wherein R1 is a tertiary butyl group and X is Br, which is prepared by the halogenation of a hindered phenol of the general Formula 3 
wherein R1 is tert-butyl with a compound having general Formula 4 
wherein R2 and R3 are C1 to C8 linear or branched alkyl.
Hindered phenols have been used as stabilizers in foodstuffs, rubber, plastics, oils etc. since long. Polymers have replaced metals, glass, ceramics and papers in packaging, automobiles, building construction, electronics, electrical equipment, furniture, pipes and heavy industrial equipments. In a nutshell, from agriculture to transport and aerospace to food packaging, the use of plastics have become integral parts of our daily life. Polymers, all natural and synthetic, in common use, are susceptible to thermal/photo-oxidative degradation upon exposure to natural and artificial weathering. The deterioration of these polymeric materials is mainly due to the heat and UV portion of sunlight reaching the earth surface. The net result of degradation is the loss in the molecular weight and macroscopic physical properties. In order to avoid this loss, different types of stabilizers have been devised that protect the polymeric substrate from detrimental effect of heat and light.
This invention relates to N,N-di substituted para-phenylene diamines as representing compound of Formula 1 which offer protection to polymers such as natural rubber and elastomers against the deteriorous effects of oxygen and ozone. It also relates to the methods for the preparation and use of these materials and to the compositions formed by mixing these materials with polymers. Para-phenylene diamines have been used as antioxidants and antiozonants since long.
Following patents and literature provide information about synthesis of the antioxidants and antiozonants and their uses. For example, U.S. Pat. No. 3,644,482 describes hindered phenol stabilizers based on esters of 3-(3,5-di-t-butyl4-hydroxyphenyl)propionate. N-alkyl, N""-phenyl-p-phenylene diamines are revealed in U.S. Pat. Nos. 3,409,586; 3,424,713; 3,542,691; 3,663,505 and 3,839,275 and British Patent No. 1,035,262. Sulphur containing para-phenylene diamines are disclosed in U.S. Pat. No. 3,035,014. In addition, aromatic amines have also been revealed in U.S. Pat. No. 3,505,225 as antioxidants based on xcex1-methylstyryl-substituted diphenylamines. In addition, U.S. Pat. Nos. 4,797,511 and 4,837,259 describe the synergistic blends of hindered phenols and amine antioxidants as stabilizers for polypropylene and polyethylene. U.S. Pat. No. 3,304,283 discloses an antioxidant composition for mono-olefinic polymers, containing at least one aromatic phenolic thioether, diaryl thioether, aliphatic disulfide, aromatic disulfide and/or aliphatic thiuramdisulfide in combination with at least one biphenol and/or aromatic amine. The mixtures of an amine component and a sterically hindered phenol component with and without other ingredients are also revealed in U.S. Pat. Nos. 3,432,578; 3,567,664; 3,637,865; 3,655,559; 5,834,544 and 5,120,844.
The one step acid catalyzed reaction with thiols, formaldehyde and aromatic amines is known in the prior art (J. Org. Chem., 24, 1035(1959); J. Org. Chem., 28, 2763(1963) and J. Org. Chem., 30, 28(1965). As known to the skilled in the art, degradation of rubber from ozone manifests itself by (i) crack appearing perpendicular to the stress in the rubber and (ii) the appearance of a silvery film on the surface of the article. The attack of ozone is a purely surface phenomenon. The function of the antiozonant depends on migration to the surface of the rubber article.
The main object of the present invention is therefore, to provide a novel antiozonant as well as antioxidant based on functionalized hindered phenol and a process for the preparation thereof, which can fulfill the prerequisites of a polymer stabilizer and can be synergistically used with other polymer stabilizers. Moreover, this class of combination of hindered phenols and diamines are known to be compatible with polyolefins, polycarbonate, polystyrene and diene-elastomers and can even be added in an additive proportion to obtain desired thermal stability of various other polymers.
The present invention provides a novel combination of antioxidant and antiozonant based on functionalized hindered phenol of the formula 1
wherein R1 is tert-butyl and R2 and R3 are C1 to C8 linear or branched alkyl.
The present invention also provides a process for the preparation of novel antioxidant cum antiozonant of the formula 1 below 
which comprises dissolving a compound of formula 3 
wherein R1 is tert-butyl, with bromine in a non polar organic solvent at a temperature in the range of 80 to 95xc2x0 C. for a period of 4 to 7 hours, evaporating the solvent under reduced pressure to obtain a compound of formula 2 
wherein R1 is a tertiary butyl group and X is Br, reacting the compound of general Formula 2 with compound of formula 4 
wherein R2 and R3 are C1 to C8 linear or branched alkyl, in presence of an organic solvent using a mild base at a temperature in the range of 80 to 95xc2x0 C. for a period of 4 to 7 hours, bringing the reaction mixture to room temperature, separating the organic layer and concentrating the product and purifying the final product of formula 1.
In one embodiment of the present invention, the neutral organic solvent used for dissolving the compound of formula 3 is a chlorinated solvent selected from the group consisting of carbon tetrachloride, chloroform, chlorobenzene and dichloromethane.
In another embodiment of the invention, the bromination of compound of formula 3 is achieved by using liquid bromine.
In still another embodiment of the invention, the para-phenylene diamine of formula 4 is selected from N,N-dimethyl-para-phenylene diamine, N,N-diethyl-para-phenylene diamine, 2,5-dimethyl-para-phenylene diamine and 2,5-diethyl-para-phenylene diamine.
In still another embodiment of the invention, the solvent used to dissolve the para-phenylene diamine is tetrahydrofuran (THF).
In still another embodiment of the invention, the inorganic base used to basify para-phenylene diamine is selected from carbonates or bicarbonates of alkali metals such as potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate.
In another embodiment of the invention, the product of formula 1 is concentrated by solvent evaporation under reduced pressure and purified by silica gel chromatography.